The program will assemble and study all known and suspected epidemiologic and genetic events, factors and attributes possibly related to risk of prostatic carcinoma, sorting out those which may directly or indirectly influence onset of the lesion. Objectives are to explore strategies for prevention and early detection of this prevalent cancer, to identify individuals at increased risk, to provide hypotheses useful in repeat studies and prospective designs, to establish a rationale for the natural history of prostatic cancer, to structure models for oncogenesis in the human prostate, to develop an information base for screening programs, and to reduce morbidity and mortality rates from this disease in the population. The research design is a collaborative retrospective matched-pair case-control study, with sampling at 3 major institutions in 2 widely separated metropolitan areas of the United States, Chicago and Los Angeles, providing multiple-hospital access to large populations of prostatic cancer patients, opportunity for reproducibility comparisons by institutions, by geography, by race and by socioeconomic level; and also full studies of 500 securely diagnosed patients against 500 cancer-free controls. Epidemiologic information is obtained with interviewer administered questionnaires and related instruments inquiring into behavioral, sociocultural, sexual, physical, psychological, clinical and anthropometric associations with risk of this carcinoma. Familial studies are conducted into 3 generations of each kinship, with patients and controls as probands, in searching for genetic influence upon initiation of oncogenesis. Sampling is under way; preliminary analysis of first results has taken place and periodic assessment of trends will continue as data develop.